Lift Foot Up (LFU) describes a behavior of a driver taking his or her foot off an accelerator pedal while the driver accelerates, or otherwise operates, a vehicle. In this case, the LFU shifting that is generally generated is upshift shifting and is generated in the situation where an input torque of a transmission is low or reduced to be low, and therefore uses a shifting clutch hydraulic control pattern called power-off upshift.
In this case, a line pressure is generally controlled to be a maximum line pressure to secure uniform shifting quality. A driver expects a feeling that a vehicle is close to neutral when he or she does not decelerate the vehicle upon the LFU shifting. In this case, a shifting control uses a method for performing shifting by reducing an oil pressure of a release side clutch to release the clutch and then increasing an oil pressure of an engagement side clutch at synchronous timing while waiting for the input shaft speed of the transmission to be reduced.
The LFU shifting releases the clutch when a torque is applied to an engine or a motor in an idle state in order to wait for a natural reduction in the input shaft speed, and therefore has a limit in reducing a length of a shifting section, or time.
As such, when the shifting section is long, the section in which the line pressure is kept high is also long, and therefore a reduction in fuel efficiency may occur.
Meanwhile, a production of a vehicle to which an electric oil pump (EOP) is applied has increased in recent years. In this case, an oil pump unit (OCU) is provided to control a driving of the EOP. The OCU receives an oil pump power value corresponding to a target line pressure calculated by a transmission control unit (TCU) to drive the EOP at a speed at which a required line pressure may be generated.
Therefore, it is possible to more efficiently form a target oil pressure of the oil pump as compared with the existing mechanical oil pump (MOP).
When the shifting control is performed, the maximum line pressure is used to minimize an effect of deviation on a hydraulic system, and thus obtain uniform shifting quality. However, when the control for increasing the line pressure to the maximum line pressure for each time shifting is performed, the shifting time is increased and the oil pump is driven, such that fuel efficiency may be reduced.
The matters described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.